Yesterday, during a break at the Barcamp Munich, I gave Wolfram a short introduction on his Mac and decided to put some stuff here [in this post]. DTrace is a toolkit available on Solaris (Solaris 10 or OpenSolaris), recent MacOS versions and FreeBSD for mightier than tools like truss or strace but with way less impact. DTrace allows you to "hook" (called "probes") into the system and allows to do some analysis then.
He shows how to set up some of these "hooks" using D-script to wrap around a simple PHP script call. He alters the results to show things like the memory function its in, how much of the memory its using and a fun little script that "graphs" out the memory usage with "@" symbols.